Emerald is a gemstone and a variety of the mineral beryl (Be3Al2(SiO3)6) coloured green by trace amounts of chromium and sometimes vanadium. Beryl has a hardness of 7.5–8 on the Mohs scale. Most emeralds are highly included, so their toughness (resistance to breakage) is classified as generally poor. It is a cyclosilicate.
The word "emerald" is derived (via Old French: esmeraude and Middle English: emeraude), from Vulgar Latin: esmaralda/esmaraldus, a variant of Latin smaragdus, which originated in Greek: σμάραγδος (smaragdos; "green gem").
Emerald is regarded as the traditional birthstone for May as well as the traditional gemstone for the astrological signs of Taurus, Gemini, and sometimes Cancer.
This post is part of the Friday Greens meme.